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Geothermal sources are found to be the most aggressive natural environments for construction materials in terms of corrosion. This study was focused on investigating the suitability of stainless steel UNS S31603 in volcanic areas of geothermal sites Sibayak and Lahendong (Indonesia). Influence of different factors (temperatures up to 175 °C, chloride content up to 1500 mg/L and pH down to 2) was assessed to determine a 'safe operating window' of a power plant and assure the system integrity. Investigations were performed by means of electrochemical methods and long-term exposure tests.
Many technologies have been developed to take advantage of geothermal energy, which became a feasible energy source to replace fossil fliel supply. Nevertheless, Service conditions in geothermal facilities are due to the Chemical composition of hydrothermal fluids and involved high temperatures, in many cases, extreme in terms of corrosion. Therefore, materials selection based on preliminary material qualification is essential to guarantee a secure and reliable Operation ofthe facilities.
This contribution deals with the evaluation of the corrosion behavior of two high-alloyed metallic materials and a-A1203 in an artificial geothermal fluid simulating the conditions in the Northern German Basin, a location with high geothermal potential. The suitability of the super austenitic stainless Steel, alloy 31, and the nickel base alloy 59 in this geothermal fluid obtained by electrochemical measurements and exposure tests is addressed. As an alternative to the suitable but costly alloy 59 that showed excelient corrosion resistance against pitting corrosion, ceramic made of a-A1203 represents an interesting possibility for selected components to be used in the construction of geothermal facilities.
The corrosion behavior of carbon Steel and different high-alloyed metals including duplex and austenitic stainless steels as well as a nickel alloy have been evaluated in artificial geothermal fluids simulating the conditions in some locations with geothermal potential in Germany, as well as two sites in Indonesia.
The suitability of low alloyed Steel UNS G41300, stainless steels UNS S31603 UNS S31803, UNS S32760 and super austenitic Steel UNSN08031 in these geothermal waters, investigated by electrochemical measurements and exposure tests, is limited. The nickel based alloy UNS N06059 shows excellent corrosion resistance against pitting corrosion. Excluding its high cost, it is a very good alternative to be used in the construction of geothermal facilities having highly sahne brines. Stainless and duplex steels exhibit a limited corrosion resistance concerning pitting and crevice corrosion.
Besides the higher alloyed materials, also the low-alloyed Steel UNS G41300 could be employed as a constructional material for the geothermal power plant in non-saline environments with moderate pH, as long as the wall thickness of the material vs. corrosion rate is taken into account.
Geothermal brines often contain high amounts of lead and copper ions that can precipitate as native Cu and Pb as consequence of galvanic corrosion when brines react with carbon steel materials. This contribution evaluates which materials could overcome the problem of galvanic corrosion at geothermal environment.
The behavior of these materials in water containing high chloride concentration (> 100 g/L NaCl) as well as various amounts of dissolved bCl2 and/or CuCl2 was characterized by electrochemical and exposure measurements.
Both methods reveal carbon steel suffers corrosion susceptibility, accompanied by Cu◦ and/or Pb◦ precipitation on the surface. Electrochemical measurements on stainless steels result in significant difference in corrosion and repassivation potentials (Ecorr = -189 mV, Erep = 70 mV), indicating a good corrosion resistance.
Since geothermal wells are a feasible energy source to replace fossil fuel supply, many technologies have been developed to take advantage of geothermal energy. Nevertheless, service conditions in geothermal facilities are due to the chemical composition of hydrothermal waters and temperatures, in many cases, extreme in terms of corrosion. Therefore, materials selection based on preliminary material qualification is essential to guarantee a secure and reliable operation of the facilities.
This contribution deals with the evaluation of the corrosion behavior of different steels in flowing low saline, slightly alkaline, artificial geothermal water simulating the conditions in the Molasse-Basin, a location with geothermal potential in Germany.
Test results for steels UNS S31603 and UNS S31803 exposed to this geothermal water obtained by electrochemical measurements and exposure tests are presented. Results obtained in static and flowing water condition show good performance of both alloys with a possible onset of localized corrosion at UNS S31603 in static conditions.
Corrosion resistance of high-alloyed and alternative materials in an artificial geothermal water
(2014)
Many technologies have been developed to take advantage of geothermal energy, which became a feasible energy source to replace fossil fuel supply. Nevertheless, service conditions in geothermal facilities are due to the chemical composition of hydrothermal fluids and involved high temperatures, in many cases, extreme in terms of corrosion. Therefore, materials selection based on preliminary material qualification is essential to guarantee a secure and reliable operation of the facilities.
This contribution deals with the evaluation of the corrosion behavior of two high-alloyed metallic materials and α-Al2O3 in an artificial geothermal fluid simulating the conditions in the Northern German Basin, a location with high geothermal potential. The suitability of the super austenitic stainless steel UNS N08031 and the nickel base alloy UNS N06059 in this geothermal fluid obtained by electrochemical measurements and exposure tests is addressed. As an alternative to the suitable but costly UNS N06059 that showed excellent corrosion resistance against pitting corrosion, ceramic made of α-Al2O3 represents an interesting possibility for selected components to be used in the construction of geothermal facilities
Geothermal energy is an interesting alternative to polluting fossil energy sources. Therefore, in Belgium, two wells have been drilled for a deep geothermal power plant. However, the environment to which the installations are exposed is challenging. The geothermal brine has 165 g/l total dissolved solids (of which 90% are sodium and chlorine) and the production temperature can be up to 130 °C. To assess their suitability to be used in a geothermal power plant, the corrosivity of the artificial brine to three common construction materials was investigated with exposure and electrochemical tests. The metals under consideration are a low-alloyed carbon steel (S235JR), an austenitic stainless steel (UNS S31603) and a duplex stainless steel (UNS S31803). The carbon steel, that was found to corrode uniformly, could be considered as a constructional material if a sufficient wall thickness is chosen. The austenitic stainless steel and the duplex stainless steel demonstrate very low uniform
corrosion rates. They are however susceptible to pitting and crevice corrosion. To guarantee safe operation of the geothermal power plant, the susceptibility of the alloys to stress corrosion cracking should be tested and in situ experiments should be performed.
Within the last years the use of geothermal energy as feasible energy source has risen and is going to replace fossil fuel supply more and more. Nevertheless, Service conditions in geothermal facilities are due to the Chemical composition of hydrothermal fluids and temperatures, in many cases, extreme in terms of corrosion. Since the construction of geothermal power plants shall be economical with maximum life Service, materials selection based on preliminary material qualification is essential to guarantee a secure and reliable Operation ofthose facilities.
The materials selection depends on the location of a power plant respectively on the Chemical composition of the produced aquifer fluid. The duplex Steel is often used as allround solution not only for the construction of geothermal power plants, because of its combination of good mechanical and corrosion properties and its lower costs compared to other highly alloyed materials. But there are limits for the use of the duplex-steel 1.4462 regarding its corrosion behavior, with which this contribution deals.
The limitations of suitability of duplex steel 1.4462 in the geothermal fluids of Molasse Basin and Upper Rhine Graben obtained by means of electrochemical measurements and exposure tests are presented below. While 1.4462 in the artificial Molasse Basin Fluid shows an excellent corrosion resistance against pitting and uniform corrosion it presents low corrosion resistance in the artificial Upper Rhine Graben Fluid due to the difference in salinity. Besides it shows a limited corrosion resistance concerning crevice corrosion.